Until recently, network devices required their own individual power supplies, either internal or external, connected to a power outlet. The introduction of the ability to deliver 7.5 Watts of power over a Category 5 (Cat 5) Ethernet cable with simultaneous transmission of data spawned the ability to provide both power and network connection to network devices. “Ethernet” is the term used for a specific local area network (LAN) architecture that is set forth in the Institute of Electrical and Electronic Engineers (IEEE) standard 802.3. A Cat 5 cable is a cable comprised of four twisted pairs of copper wires terminated with RJ45 connectors. The network devices that may take advantage of this power include Voice of Internet Protocol (VoIP) phones, wireless access points, and web cameras, among many others. The transmission of power through the Cat 5 cable is also referred to as Power over Ethernet, or PoE.
An even newer innovation is the ability to provide power up to 15.3 W, set out in the IEEE standard 802.3af. This power is delivered to a specially designed Ethernet switch that injects the power between the cable and the switching device. As a device is connected to a port on the switch, a negotiation takes place that defines the type of device and the wattage required, with low wattage currently being defined as 7.5 W, high wattage as 15.3 W. The actual wattage used by the device may vary depending upon the functions on the device in use at any given time. Other devices may use this extra wattage.